Dendrimers decorated with the HLA-DR epitope, PADRE, comprise a vaccine platform (PDD). This modified platform can deliver high quantities of conjugated cargo specifically to MHC class II-expressing antigen-presenting cells (APCs), including dendritic cells, macrophages, and B cells of multiple species. Here, the PDD platform is conjugated to a hapten, cocaine, demonstrating durable anti-hapten immunity. PDD vaccine generates high-affinity cocaine antibodies without the need for an adjuvant. Adjuvant formulations of the PDD vaccine do not increase further anti-cocaine titer levels. PDD-elicited anti-cocaine antibody response attenuates the rewarding effects of cocaine in adult male Sprague-Dawley rats.